Method of Forming a Circular Sheet-Metal Blank

ABSTRACT

A method of forming a circular sheet-metal blank which rests on a tool rotating about an axis. The sheet-metal blank has a thickness and has a diameter which is small than a diameter of the tool.

BACKGROUND AND SUMMARY

The present disclosure relates to a method of forming a circular sheet-metal blank which has a central hole and rests on a tool rotating about an axis. The sheet-metal blank has a thickness and has a diameter which is smaller than a diameter of the tool.

The present disclosure relates to a method of forming circular sheet-metal blanks by flow-forming rollers.

The present disclosure relates to a method of forming a circular sheet-metal blank which rests on a tool rotating about an axis. The sheet-metal blank has a thickness and has a diameter which is smaller than a diameter of the tool.

In forming the sheet-metal blank, one or more flow-forming rollers are plunged axially into the material of the circular sheet-metal blank and are moved radially outward. That is, the path of the flow-forming rollers includes at least one component motion in the radial direction. As a result, the area of the circular sheet-metal blank is enlarged radially in all directions. Consequently, a rotationally symmetrical part, in particular a circular sheet-metal blank having a larger diameter d2 and a thickness a2 reduced at least in sections or throughout, is produced from the circular sheet-metal blank having an initial diameter d1 and a thickness a1.

In accordance with the present disclosure, it is possible to produce a circular sheet-metal blank, or directly a rotationally symmetrical part such as a gear part, having a larger diameter d2 and a thickness a2 reduced at least in sections or throughout, from a circular sheet-metal blank having an initial diameter d1 and a thickness a1. It is even possible to increase the diameter by more than 10%, in particular by more than 20%.

The expression “circular sheet-metal blank” must not be considered too narrowly with regard to the part produced by the forming. Firstly, it is possible to produce a flat circular sheet-metal blank. However, said blank may also be contoured if the tool is correspondingly contoured. In addition, the circular sheet-metal blank may be machined or further processed to directly produce a gear part or the like.

The method, according to the present disclosure, can be used in a wide variety of sectors. A preferred embodiment is the enlargement of “small” circular sheet-metal blanks as occur, for example, more or less as waste in the manufacture of wheel disks for trucks, which waste otherwise ought to be scrapped. However, it is also possible, according to the present disclosure, to use the method for another purpose, e.g. for producing wheel disks for smaller utility vehicles. The cost advantage which can be achieved in this way should not be underestimated.

Alternatively, it is possible to directly provide an essentially rotationally symmetrical part of virtually any desired type from a circular blank of larger initial thickness, said part having a region of smaller thickness and a larger diameter. Possible applications also arise in the field of flywheel ring gears. In the case of all these parts, novel solution approaches which considerably reduce, for example, the material scrap and thus the production costs are obtained by the method according to the present disclosure.

It is known that a circular blank widens somewhat during the plunging of a flow-forming roller, for example, during the integral forming of a hub. But the widening is only a secondary effect which leads to the clamping of the circular blank on an abutment chuck. In addition, the circular blank is not moved radially outward but rather radially inward, such that no specific widening, in particular not by more than percentage specifications, disclosed later in the present disclosure, is effected.

Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a circular metal blank as an initial workpiece, according to the present disclosure.

FIG. 2 shows the circular metal blank of FIG. 1 on a tool, represented by dashed-lines and after forming, represented by solid lines.

DETAILED DESCRIPTION

FIG. 1 shows a circular sheet-metal blank 1 having a central hole 2. The circular sheet-metal blank 1, as shown in FIG. 2, rests on a tool 4 which rests on a spindle (not shown) of a flow-forming machine and rotatable about an axis 3. The sheet-metal blank 1 has a thickness a1 and a diameter d1.

The circular sheet-metal blank 1 is held at the central hole 2. To this end, at least one pin 5 engages in the central hole 2, which may be in a clamping manner. A counterholder device 6, which has a larger diameter than the central hole 2, can adjoin pin 5 on a side of the circular sheet-metal blank 1 which faces away from the tool 4. An axial length of the pin 5 may be smaller than, just as large as or larger than the thickness d1 of the circular sheet-metal blank 1. The circular sheet-metal blank 1 may be made of a cast iron or another metal which can be formed by flow forming.

The tool 4 extends radially in all directions beyond an outer circumference of the circular sheet-metal blank 1 which may have a circular form. The sheet-metal blank 1 preferably has a flat surface, but may also be of contoured design.

One or more freely rotatable flow-forming rollers 7 are arranged above the circular sheet-metal blank 1. The rollers 7 can also be fed-in in superimposed movements at least axially in a direction x toward the sheet-metal blank 1, or workpiece, and radially in a direction r.

As soon as the tool 4, together with the circular sheet-metal blank 1, has reached a predetermined rotational speed, the flow-forming roller 7 is fed-in axially in the direction x at a distance from an outer circumference, preferably close to the central hole 2 or even at the edge of the central hole 2. In the course of being fed, the roller 7 plunges into the sheet-metal blank 1, or workpiece. After that, or at the same time, the roller 7 is moved outward radially in the direction r, such that the roller 7 presses or pushes the material of the circular sheet-metal blank 1 radially outward ahead of it. In this way, the area of the circular blank 1 is enlarged radially in all directions, and surprisingly without crack formation in the outer circumferential region.

This operation is repeated several times.

A freely rotatable hold-down roller 8 in the outer circumferential region can additionally prevent the material of the sheet-metal blank 1 from arching forwards from a plane of the circular sheet-metal blank 1.

The method, according to the present disclosure, includes producing waste parts or waste circular blanks used in wheel tire production. The method, according to the present disclosure, further includes producing gear parts and flywheel ring gears having larger diameters than the diameter of the initial circular blank.

Although the present disclosure has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present disclosure is to be limited only by the terms of the appended claims. 

1. A method of forming a circular sheet-metal blank, the method steps comprising: providing a tool rotatable about an axis, the tool having a tool diameter; providing a circular sheet-metal blank, the sheet-metal blank resting on the tool and having an initial thickness and an initial diameter that is smaller than the tool diameter; providing a flow-forming roller; plunging the free-forming roller into material of the circular sheet-metal blank; and moving the free-forming roller radially outward such that an area of the circular sheet-metal blank is enlarged radially in all directions to form a rotationally symmetrical circular sheet-metal blank having a resulting thickness that is smaller than the initial thickness at least in sections of the sheet-metal blank and a resulting diameter that is larger than the initial diameter.
 2. The method according to claim 1, wherein the circular sheet-metal blank includes a central holes.
 3. The method according to claim 1, wherein the circular sheet-metal blank is held on the tool.
 4. The method according to claim 1, wherein the moving of the flow-forming roller radially outward is repeated several times.
 5. The according to claim 1, wherein the resulting diameter is larger than the initial diameter by more than 5%.
 6. The method according to claim 1, wherein the resulting diameter is larger than the initial diameter by more than 10%.
 7. The method according to claim 1, wherein the resulting diameter is larger than the initial diameter by more than 20%.
 8. The method according to claim 1, wherein a drifting of the material of the circular sheet-metal blank in the axial direction is prevented by one or more freely rotatable hold-down rollers.
 9. (canceled)
 10. The method according to claim 1, wherein the formed symmetrical sheet-metal blank includes a waste circular blank used in wheel tire production.
 11. The method according to claim 1, wherein the formed symmetrical sheet-metal blank includes a gear part.
 12. The method according to claim 1, wherein the formed symmetrical sheet-metal blank includes a flywheel ring gear.
 13. The method according to claim 1, further including the step of providing a plurality of flow-forming rollers. 